Diagnostic certainty

Diagnostic certainty is a component of all cases and reflects how well the diagnosis has been established. It ranges from "possible" to "certain" and it is crucial that the certainty of a diagnosis is not overstated. Doing so only reduces the utility of the Radiopaedia case library and undermines your own credibility as a contributor. 

Please be pedantic and skeptical of your own cases and strive to establish the diagnosis with supporting information. 

Which diagnostic certainly level applies?

It is difficult to have a dogmatic definition for each level (see below) as this largely depends on the case. A good rule of thumb is to ask yourself this:

"Would a pedantic high-end peer-reviewed journal accept the diagnosis if you submitted it as a case report?"

In other words, would a cynical and skeptical third party agree that there was no doubt whatsoever about the diagnosis? Only if your honest answer is "yes" then, and only then, can the diagnosis be considered "Certain". 

This is especially true for rare, atypical or generally unusual cases. Remembering a saying popularized by Carl Sagan "Extraordinary claims require extraordinary evidence" ³. Before we can accept a diagnostic certainty of "certain" or "almost certain" we need you to mount a compelling case, and in such instances, it will require histology reports or slides, operative photos etc.

And remember, just because you feel certain does not mean you are right. This is particularly the case if you are straying outside of your comfort zone (i.e. you are relatively junior, it is an unusual case, it is outside of your area of expertise etc.). Whatever you do don't forget the Dunning-Kruger effect ^1,2, which is all too alive and well in medicine. 

Specific well-established criteria exist for a few conditions (e.g. Boston criteria 2.0 for cerebral amyloid angiopathy) and these criteria should be followed to set the diagnostic certainty on Radiopaedia.

Where is diagnostic certainty located

The user interface to set Diagnostic certainty (DC) is visible immediately below the title in case edit mode. It comprises a slider, with descriptions of each state. 

The status of cases is indicated with a colored dot (see below). 

There are 5 possible levels of diagnostic certainty 

1. Possible (red dot)

   • the preferred diagnosis is one of a number of possible diagnoses, and although it is perhaps more likely, other conditions remain viable alternatives

   • cases like this are only sometimes worthwhile, but often they are not

   • if you want to publish it anyway, you need to include a discussion on why you favor a particular diagnosis

   • be prepared for your case to be rejected for publication; that's ok, you can always keep it as one of your unlisted cases

   • NB: it is likely that in the future we will filter out "possible" cases from search results

2. Probable (orange dot)

   • the preferred diagnosis is far more likely (>90%) than any alternative, but the diagnosis has not been established

   • NB: it is likely that in the future we will filter out "probable" cases from search results

3. Almost certain (yellow dot)

   • you have good reasons to believe the diagnosis was confirmed, but you do not have direct access to the proof and cannot upload it

   • examples: 

     • you collected this case some time ago and have included "path proven" in the description but not the actual histology report

     • a secondary source states the diagnosis (e.g. the referral, or the treating unit or a colleague tells you the result of a biopsy) but you haven't seen the report yourself

   • imaging is almost pathognomonic but it is conceivable that an unusual-appearing other entity could have similar appearances

   • examples:  

     • adrenal myelolipoma has a very characteristic appearance but it is conceivable that an unusual appearing retroperitoneal liposarcoma could appear similar

4. Certain (green dot)

   • the diagnosis is 100% certain based on:

     • unequivocal or pathognomonic imaging appearance

     • Aunt Minnies are not always pathognomonic

     • clinical, surgical or pathological proof directly obtained from a primary source by the uploader (e.g. directly from the histology report)

   • where appropriate you should include substantiating evidence (e.g. histology report/slides, diagnostic laboratory test/values)

   • Not sure? Ask yourself this: "Would a journal accept the diagnosis if you submitted it as a case report?" In other words, would a cynical and skeptical third party agree that there was no doubt about the diagnosis? Only if your honest answer is "yes" then should the diagnosis be considered "Certain". 

5. Not applicable (no dot)

   • the images are not of a patient with a particular diagnosis

   • examples:

     • normal scan for teaching purposes

     • diagrams, illustrations, or flow chart

How diagnostic certainty is used on the site

The diagnostic certainty of a case has many implications and functions. 

Firstly it has a strong influence on case completeness, and therefore when sorting search results by case completeness, cases with high DC will be favored. Similarly, these cases will be more frequently shown in Quiz Mode. 

Secondly, search results will show the DC level as a colored dot (matching the slider). 

Thirdly, search results may be filtered to only show cases of a minimum DC (e.g. "Almost certain").